1. Field of the Invention
The present invention relates to an amorphous organic thin-film element and an amorphous organic polymer composition for use in various applications.
2. Description of the Related Art
Recently, various types of electronic devices using ultra thin films of organic substances have been extensively researched. Among other organic thin films, an amorphous thin film is very important in transparency, homogeneity, and stability because the film has no grain boundary. As an example, an organic photoconductor (OPC) used in a Carlson process employs an amorphous thin film in which a charge-generation agent or a charge-transport agent is dispersed or dissolved homogeneously in an amorphous polymer. As for very thin films of organic substances represented by a Langmuir-Blodgett film (LB film), an amorphous LB film consisting of a polymer or a dye is more homogeneous than a crystalline LB film consisting of an aliphatic acid and therefore has good properties as an ultra thin insulating film (e.g., Published Unexamined Japanese Patent Application No. 63-166261). In addition, electroluminescence (EL) elements using vapor-deposited films of organic substances have been developed in recent years (e.g., Published Unexamined Japanese Patent Application Nos. 57-51781, 59-194393, and 63-295695). In the case of these elements, a thin film with a film thickness of about 10 nm is required in order to decrease the application voltage. For this reason, an amorphous thin film is used to obtain an element which can withstand a vapor deposition process for an upper electrode, causes no electrical short circuit, and has a high operating stability. Organic thin films which can transport electrons or holes efficiently are necessary for organic photovoltaic cells or organic rectifying elements as well as the organic electrophotographic photosensitive bodies or the organic EL elements described above, and so a demand has also arisen for stable amorphous thin films for use in these electronic elements. Furthermore, amorphous organic polymer compositions in which dye molecules are contained in amorphous polymers are used not only as bulk materials but as thin films in the organic photoconductors described above, photosensitive resist thin films, optical switching elements using optical waveguides, and optical disks. The amorphous organic polymer compositions are also widely used as a variety of coating thin films.
Almost no thin films consisting of low-molecular materials, however, unlike thin films using polymers, have been put into practical use as amorphous thin films for electronic devices. The major cause of this is that many of low molecular weight materials have low glass transition temperatures (Tg) and hence are low in heat resistances, so crystallization is encouraged by heat generated when elements are driven, resulting in easy occurrence of degradation. In addition, in the case of a system in which dye molecules are contained in a polymer, if amorphous dye molecules having a low Tg are used in such a system, the Tg of the whole system decreases to lead to a decrease in heat resistance. Note that in such a system, although mixing of crystalline dye molecules into a polymer can prevent the decrease in Tg, the dye concentration cannot be raised because a homogeneous dispersion state is difficult to obtain. Note also that the heat resistance can be improved by chemically bonding the dye molecules to the polymer, but this is accompanied by a difficulty in synthesis.